Characterisation of Almadén mercury mine environment by XAS techniques

Abstract

This manuscript describes the analysis and evaluation of mercury species present in three different types of samples (ore, slag and soil) belonging to the abandoned mining area of Almadén (Spain), by means of X-ray Absorption Spectroscopy (XAS) techniques. The applied methodology includes the analysis of possible interfering compounds by ICP-OES and the characterisation of solid samples by identification of heterogeneities using SEM-EDS technique prior to measurements at the synchrotron facilities (ESRF in Grenoble, France and HASYLAB in Hamburg, Germany) and subsequent analysis of data. Results show that cinnabar is the main species both in ore and soil samples, its concentration ranging from 41 to 77% of the total mercury content. On the other hand, metacinnabar (a polymorph of cinnabar) is shown to be the main species in slag samples (42–88%). Other mercury forms have been found in minor proportions (<30%), such as slightly soluble mercury salts (HgCl₂ and HgSO₄) and HgO. This is the first time that Almadén-type mercury ores have been characterised by a synchrotron-based spectroscopic technique for a direct determination of mercury species. The conclusions presented in this report show the important similarities between Almadén and hot-spring type mercury mineral deposits, despite its different geological origin.